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	$104.46	10.826%	$115.7688	$115.77	$115.75	$115.80
Purchase #2	$103.81	7.250%	$111.3362	$111.34	$111.35	$111.30
Purchase #3	$74.83	11.570%	$83.4878	$83.49	$83.50	$83.50
Purchase #4	$55.25	5.673%	$58.3843	$58.38	$58.40	$58.40
Purchase #5	$81.97	9.518%	$89.7719	$89.77	$89.75	$89.80
Purchase #6	$132.43	4.476%	$138.3576	$138.36	$138.35	$138.40
Purchase #7	$145.32	6.502%	$154.7687	$154.77	$154.75	$154.80
7 purchase totals =	$698.07		$751.8753	$751.88	$751.85	$752.00