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	$115.50	7.825%	$124.5379	$124.54	$124.55	$124.50
Purchase #2	$80.30	6.419%	$85.4545	$85.45	$85.45	$85.50
Purchase #3	$230.72	8.113%	$249.4383	$249.44	$249.45	$249.40
Purchase #4	$48.71	5.687%	$51.4801	$51.48	$51.50	$51.50
Purchase #5	$245.66	3.369%	$253.9363	$253.94	$253.95	$253.90
Purchase #6	$158.46	4.206%	$165.1248	$165.12	$165.10	$165.10
Purchase #7	$135.89	3.227%	$140.2752	$140.28	$140.30	$140.30
7 purchase totals =	$1,015.24		$1,070.2471	$1,070.25	$1,070.30	$1,070.20