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	$113.33	10.210%	$124.901	$124.90	$124.90	$124.90
Purchase #2	$138.89	11.362%	$154.6707	$154.67	$154.65	$154.70
Purchase #3	$165.71	13.172%	$187.5373	$187.54	$187.55	$187.50
Purchase #4	$93.28	6.553%	$99.3926	$99.39	$99.40	$99.40
Purchase #5	$117.58	8.446%	$127.5108	$127.51	$127.50	$127.50
Purchase #6	$243.67	5.592%	$257.296	$257.30	$257.30	$257.30
Purchase #7	$139.34	4.374%	$145.4347	$145.43	$145.45	$145.40
7 purchase totals =	$1,011.80		$1,096.7431	$1,096.74	$1,096.75	$1,096.70