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	$175.70	7.442%	$188.7756	$188.78	$188.80	$188.80
Purchase #2	$165.29	10.397%	$182.4752	$182.48	$182.50	$182.50
Purchase #3	$53.74	6.500%	$57.2331	$57.23	$57.25	$57.20
Purchase #4	$225.90	10.729%	$250.1368	$250.14	$250.15	$250.10
Purchase #5	$71.73	9.767%	$78.7359	$78.74	$78.75	$78.70
Purchase #6	$221.74	7.113%	$237.5124	$237.51	$237.50	$237.50
Purchase #7	$5.82	10.839%	$6.4508	$6.45	$6.45	$6.50
7 purchase totals =	$919.92		$1,001.3198	$1,001.33	$1,001.40	$1,001.30