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	$224.74	12.824%	$253.5607	$253.56	$253.55	$253.60
Purchase #2	$98.76	12.817%	$111.4181	$111.42	$111.40	$111.40
Purchase #3	$106.79	8.213%	$115.5607	$115.56	$115.55	$115.60
Purchase #4	$195.92	13.857%	$223.0686	$223.07	$223.05	$223.10
Purchase #5	$163.56	11.663%	$182.636	$182.64	$182.65	$182.60
Purchase #6	$154.34	8.424%	$167.3416	$167.34	$167.35	$167.30
Purchase #7	$18.90	9.220%	$20.6426	$20.64	$20.65	$20.60
7 purchase totals =	$963.01		$1,074.2283	$1,074.23	$1,074.20	$1,074.20