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	$86.94	3.457%	$89.9455	$89.95	$89.95	$89.90
Purchase #2	$184.27	6.747%	$196.7027	$196.70	$196.70	$196.70
Purchase #3	$131.58	6.316%	$139.8906	$139.89	$139.90	$139.90
Purchase #4	$212.34	4.157%	$221.167	$221.17	$221.15	$221.20
Purchase #5	$108.83	12.216%	$122.1247	$122.12	$122.10	$122.10
Purchase #6	$142.77	11.532%	$159.2342	$159.23	$159.25	$159.20
Purchase #7	$191.60	8.176%	$207.2652	$207.27	$207.25	$207.30
7 purchase totals =	$1,058.33		$1,136.3299	$1,136.33	$1,136.30	$1,136.30