Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$161.60	12.150%	$181.2344	$181.23	$181.25	$181.20
Purchase #2	$173.70	4.218%	$181.0267	$181.03	$181.05	$181.00
Purchase #3	$115.54	7.831%	$124.5879	$124.59	$124.60	$124.60
Purchase #4	$232.82	7.303%	$249.8228	$249.82	$249.80	$249.80
Purchase #5	$128.47	11.552%	$143.3109	$143.31	$143.30	$143.30
Purchase #6	$167.41	7.676%	$180.2604	$180.26	$180.25	$180.30
Purchase #7	$144.46	12.711%	$162.8223	$162.82	$162.80	$162.80
7 purchase totals =	$1,124.00		$1,223.0654	$1,223.06	$1,223.05	$1,223.00