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	$151.83	9.552%	$166.3328	$166.33	$166.35	$166.30
Purchase #2	$6.81	4.865%	$7.1413	$7.14	$7.15	$7.10
Purchase #3	$58.63	6.576%	$62.4855	$62.49	$62.50	$62.50
Purchase #4	$122.48	4.250%	$127.6854	$127.69	$127.70	$127.70
Purchase #5	$166.77	12.525%	$187.6579	$187.66	$187.65	$187.70
Purchase #6	$51.32	4.177%	$53.4636	$53.46	$53.45	$53.50
Purchase #7	$226.80	10.381%	$250.3441	$250.34	$250.35	$250.30
7 purchase totals =	$784.64		$855.1106	$855.11	$855.15	$855.10