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	$90.87	5.815%	$96.1541	$96.15	$96.15	$96.20
Purchase #2	$135.76	13.395%	$153.9451	$153.95	$153.95	$153.90
Purchase #3	$196.49	7.791%	$211.7985	$211.80	$211.80	$211.80
Purchase #4	$46.41	12.676%	$52.2929	$52.29	$52.30	$52.30
Purchase #5	$161.73	3.590%	$167.5361	$167.54	$167.55	$167.50
Purchase #6	$195.53	4.587%	$204.499	$204.50	$204.50	$204.50
Purchase #7	$190.50	10.387%	$210.2872	$210.29	$210.30	$210.30
7 purchase totals =	$1,017.29		$1,096.5129	$1,096.52	$1,096.55	$1,096.50