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	$176.34	6.763%	$188.2659	$188.27	$188.25	$188.30
Purchase #2	$166.76	13.626%	$189.4827	$189.48	$189.50	$189.50
Purchase #3	$50.73	12.399%	$57.02	$57.02	$57.00	$57.00
Purchase #4	$172.65	12.649%	$194.4885	$194.49	$194.50	$194.50
Purchase #5	$147.35	12.213%	$165.3459	$165.35	$165.35	$165.30
Purchase #6	$187.32	13.611%	$212.8161	$212.82	$212.80	$212.80
Purchase #7	$27.50	13.194%	$31.1284	$31.13	$31.15	$31.10
7 purchase totals =	$928.65		$1,038.5475	$1,038.56	$1,038.55	$1,038.50