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	$141.40	10.424%	$156.1395	$156.14	$156.15	$156.10
Purchase #2	$149.80	4.187%	$156.0721	$156.07	$156.05	$156.10
Purchase #3	$242.75	10.344%	$267.8601	$267.86	$267.85	$267.90
Purchase #4	$117.84	8.731%	$128.1286	$128.13	$128.15	$128.10
Purchase #5	$130.44	3.409%	$134.8867	$134.89	$134.90	$134.90
Purchase #6	$89.81	7.695%	$96.7209	$96.72	$96.70	$96.70
Purchase #7	$133.86	13.506%	$151.9391	$151.94	$151.95	$151.90
7 purchase totals =	$1,005.90		$1,091.7470	$1,091.75	$1,091.75	$1,091.70