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	$71.89	5.381%	$75.7584	$75.76	$75.75	$75.80
Purchase #2	$150.56	13.578%	$171.003	$171.00	$171.00	$171.00
Purchase #3	$168.69	5.817%	$178.5027	$178.50	$178.50	$178.50
Purchase #4	$244.41	11.591%	$272.7396	$272.74	$272.75	$272.70
Purchase #5	$196.65	10.316%	$216.9364	$216.94	$216.95	$216.90
Purchase #6	$134.91	7.363%	$144.8434	$144.84	$144.85	$144.80
Purchase #7	$106.54	5.650%	$112.5595	$112.56	$112.55	$112.60
7 purchase totals =	$1,073.65		$1,172.3430	$1,172.34	$1,172.35	$1,172.30