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	$141.70	5.186%	$149.0486	$149.05	$149.05	$149.00
Purchase #2	$103.74	7.398%	$111.4147	$111.41	$111.40	$111.40
Purchase #3	$67.66	5.347%	$71.2778	$71.28	$71.30	$71.30
Purchase #4	$52.52	7.663%	$56.5446	$56.54	$56.55	$56.50
Purchase #5	$131.54	4.744%	$137.7803	$137.78	$137.80	$137.80
Purchase #6	$54.74	6.598%	$58.3517	$58.35	$58.35	$58.40
Purchase #7	$148.95	12.462%	$167.5121	$167.51	$167.50	$167.50
7 purchase totals =	$700.85		$751.9298	$751.92	$751.95	$751.90