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	$139.88	8.665%	$152.0006	$152.00	$152.00	$152.00
Purchase #2	$243.75	4.614%	$254.9966	$255.00	$255.00	$255.00
Purchase #3	$115.73	10.216%	$127.553	$127.55	$127.55	$127.60
Purchase #4	$119.96	4.799%	$125.7169	$125.72	$125.70	$125.70
Purchase #5	$189.34	12.700%	$213.3862	$213.39	$213.40	$213.40
Purchase #6	$18.45	13.211%	$20.8874	$20.89	$20.90	$20.90
Purchase #7	$71.83	10.393%	$79.2953	$79.30	$79.30	$79.30
7 purchase totals =	$898.94		$973.8360	$973.85	$973.85	$973.90