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	$180.93	8.360%	$196.0557	$196.06	$196.05	$196.10
Purchase #2	$85.88	12.829%	$96.8975	$96.90	$96.90	$96.90
Purchase #3	$236.39	7.567%	$254.2776	$254.28	$254.30	$254.30
Purchase #4	$16.76	5.684%	$17.7126	$17.71	$17.70	$17.70
Purchase #5	$57.40	3.369%	$59.3338	$59.33	$59.35	$59.30
Purchase #6	$130.62	13.140%	$147.7835	$147.78	$147.80	$147.80
Purchase #7	$51.98	9.387%	$56.8594	$56.86	$56.85	$56.90
7 purchase totals =	$759.96		$828.9201	$828.92	$828.95	$829.00