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	$106.52	8.362%	$115.4272	$115.43	$115.45	$115.40
Purchase #2	$88.33	7.649%	$95.0864	$95.09	$95.10	$95.10
Purchase #3	$169.65	9.208%	$185.2714	$185.27	$185.25	$185.30
Purchase #4	$19.44	6.604%	$20.7238	$20.72	$20.70	$20.70
Purchase #5	$59.35	11.498%	$66.1741	$66.17	$66.15	$66.20
Purchase #6	$137.40	10.377%	$151.658	$151.66	$151.65	$151.70
Purchase #7	$102.74	6.112%	$109.0195	$109.02	$109.00	$109.00
7 purchase totals =	$683.43		$743.3604	$743.36	$743.30	$743.40