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	$133.81	10.809%	$148.2735	$148.27	$148.25	$148.30
Purchase #2	$215.89	10.433%	$238.4138	$238.41	$238.40	$238.40
Purchase #3	$193.98	12.746%	$218.7047	$218.70	$218.70	$218.70
Purchase #4	$157.66	9.480%	$172.6062	$172.61	$172.60	$172.60
Purchase #5	$123.60	3.270%	$127.6417	$127.64	$127.65	$127.60
Purchase #6	$69.66	13.430%	$79.0153	$79.02	$79.00	$79.00
Purchase #7	$169.60	5.108%	$178.2632	$178.26	$178.25	$178.30
7 purchase totals =	$1,064.20		$1,162.9184	$1,162.91	$1,162.85	$1,162.90