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	$91.40	5.171%	$96.1263	$96.13	$96.15	$96.10
Purchase #2	$23.65	3.449%	$24.4657	$24.47	$24.45	$24.50
Purchase #3	$77.82	6.548%	$82.9157	$82.92	$82.90	$82.90
Purchase #4	$184.66	5.429%	$194.6852	$194.69	$194.70	$194.70
Purchase #5	$136.32	3.651%	$141.297	$141.30	$141.30	$141.30
Purchase #6	$238.72	12.605%	$268.8107	$268.81	$268.80	$268.80
Purchase #7	$247.41	4.520%	$258.5929	$258.59	$258.60	$258.60
7 purchase totals =	$999.98		$1,066.8935	$1,066.91	$1,066.90	$1,066.90