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	$146.53	9.517%	$160.4753	$160.48	$160.50	$160.50
Purchase #2	$74.38	5.560%	$78.5155	$78.52	$78.50	$78.50
Purchase #3	$47.68	3.566%	$49.3803	$49.38	$49.40	$49.40
Purchase #4	$9.80	7.446%	$10.5297	$10.53	$10.55	$10.50
Purchase #5	$170.77	5.107%	$179.4912	$179.49	$179.50	$179.50
Purchase #6	$215.32	12.801%	$242.8831	$242.88	$242.90	$242.90
Purchase #7	$127.91	3.776%	$132.7399	$132.74	$132.75	$132.70
7 purchase totals =	$792.39		$854.0150	$854.02	$854.10	$854.00