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	$134.33	6.385%	$142.907	$142.91	$142.90	$142.90
Purchase #2	$165.56	13.549%	$187.9917	$187.99	$188.00	$188.00
Purchase #3	$61.26	13.873%	$69.7586	$69.76	$69.75	$69.80
Purchase #4	$114.95	9.456%	$125.8197	$125.82	$125.80	$125.80
Purchase #5	$145.45	4.782%	$152.4054	$152.41	$152.40	$152.40
Purchase #6	$157.30	9.121%	$171.6473	$171.65	$171.65	$171.60
Purchase #7	$158.53	6.217%	$168.3858	$168.39	$168.40	$168.40
7 purchase totals =	$937.38		$1,018.9155	$1,018.93	$1,018.90	$1,018.90