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	$84.32	4.281%	$87.9297	$87.93	$87.95	$87.90
Purchase #2	$165.44	4.250%	$172.4712	$172.47	$172.45	$172.50
Purchase #3	$73.47	5.774%	$77.7122	$77.71	$77.70	$77.70
Purchase #4	$162.31	5.413%	$171.0958	$171.10	$171.10	$171.10
Purchase #5	$153.34	11.557%	$171.0615	$171.06	$171.05	$171.10
Purchase #6	$230.73	5.360%	$243.0971	$243.10	$243.10	$243.10
Purchase #7	$134.33	4.697%	$140.6395	$140.64	$140.65	$140.60
7 purchase totals =	$1,003.94		$1,064.0070	$1,064.01	$1,064.00	$1,064.00