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	$153.78	7.644%	$165.5349	$165.53	$165.55	$165.50
Purchase #2	$92.52	7.715%	$99.6579	$99.66	$99.65	$99.70
Purchase #3	$179.83	6.615%	$191.7258	$191.73	$191.75	$191.70
Purchase #4	$91.33	9.617%	$100.1132	$100.11	$100.10	$100.10
Purchase #5	$82.34	4.307%	$85.8864	$85.89	$85.90	$85.90
Purchase #6	$250.72	5.542%	$264.6149	$264.61	$264.60	$264.60
Purchase #7	$197.39	5.809%	$208.8564	$208.86	$208.85	$208.90
7 purchase totals =	$1,047.91		$1,116.3895	$1,116.39	$1,116.40	$1,116.40