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	$193.38	6.121%	$205.2168	$205.22	$205.20	$205.20
Purchase #2	$232.90	13.164%	$263.559	$263.56	$263.55	$263.60
Purchase #3	$51.36	11.559%	$57.2967	$57.30	$57.30	$57.30
Purchase #4	$185.51	7.344%	$199.1339	$199.13	$199.15	$199.10
Purchase #5	$104.63	8.125%	$113.1312	$113.13	$113.15	$113.10
Purchase #6	$89.56	12.320%	$100.5938	$100.59	$100.60	$100.60
Purchase #7	$79.56	3.276%	$82.1664	$82.17	$82.15	$82.20
7 purchase totals =	$936.90		$1,021.0978	$1,021.10	$1,021.10	$1,021.10