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	$61.51	8.513%	$66.7463	$66.75	$66.75	$66.70
Purchase #2	$201.49	4.186%	$209.9244	$209.92	$209.90	$209.90
Purchase #3	$82.83	4.155%	$86.2716	$86.27	$86.25	$86.30
Purchase #4	$52.98	4.472%	$55.3493	$55.35	$55.35	$55.30
Purchase #5	$102.72	6.765%	$109.669	$109.67	$109.65	$109.70
Purchase #6	$133.28	12.590%	$150.06	$150.06	$150.05	$150.10
Purchase #7	$31.72	13.811%	$36.1008	$36.10	$36.10	$36.10
7 purchase totals =	$666.53		$714.1214	$714.12	$714.05	$714.10