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	$176.44	11.167%	$196.1431	$196.14	$196.15	$196.10
Purchase #2	$151.50	3.174%	$156.3086	$156.31	$156.30	$156.30
Purchase #3	$122.42	11.514%	$136.5154	$136.52	$136.50	$136.50
Purchase #4	$56.56	9.826%	$62.1176	$62.12	$62.10	$62.10
Purchase #5	$51.47	6.791%	$54.9653	$54.97	$54.95	$55.00
Purchase #6	$53.71	7.653%	$57.8204	$57.82	$57.80	$57.80
Purchase #7	$66.35	6.407%	$70.601	$70.60	$70.60	$70.60
7 purchase totals =	$678.45		$734.4714	$734.48	$734.40	$734.40