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	$191.91	12.514%	$215.9256	$215.93	$215.95	$215.90
Purchase #2	$220.67	6.417%	$234.8304	$234.83	$234.85	$234.80
Purchase #3	$76.72	3.611%	$79.4904	$79.49	$79.50	$79.50
Purchase #4	$80.39	10.814%	$89.0834	$89.08	$89.10	$89.10
Purchase #5	$71.63	12.465%	$80.5587	$80.56	$80.55	$80.60
Purchase #6	$100.85	8.756%	$109.6804	$109.68	$109.70	$109.70
Purchase #7	$60.95	7.567%	$65.5621	$65.56	$65.55	$65.60
7 purchase totals =	$803.12		$875.1310	$875.13	$875.20	$875.20