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	$107.59	9.498%	$117.8089	$117.81	$117.80	$117.80
Purchase #2	$117.94	7.442%	$126.7171	$126.72	$126.70	$126.70
Purchase #3	$220.88	11.165%	$245.5413	$245.54	$245.55	$245.50
Purchase #4	$250.47	13.810%	$285.0599	$285.06	$285.05	$285.10
Purchase #5	$63.62	12.349%	$71.4764	$71.48	$71.50	$71.50
Purchase #6	$158.28	4.444%	$165.314	$165.31	$165.30	$165.30
Purchase #7	$147.61	13.214%	$167.1152	$167.12	$167.10	$167.10
7 purchase totals =	$1,066.39		$1,179.0328	$1,179.04	$1,179.00	$1,179.00