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	$105.76	4.119%	$110.1163	$110.12	$110.10	$110.10
Purchase #2	$119.36	10.495%	$131.8868	$131.89	$131.90	$131.90
Purchase #3	$154.58	3.432%	$159.8852	$159.89	$159.90	$159.90
Purchase #4	$49.61	10.424%	$54.7813	$54.78	$54.80	$54.80
Purchase #5	$130.48	7.201%	$139.8759	$139.88	$139.90	$139.90
Purchase #6	$205.76	6.846%	$219.8463	$219.85	$219.85	$219.80
Purchase #7	$157.41	6.415%	$167.5079	$167.51	$167.50	$167.50
7 purchase totals =	$922.96		$983.8997	$983.92	$983.95	$983.90