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	$29.53	11.166%	$32.8273	$32.83	$32.85	$32.80
Purchase #2	$62.91	11.645%	$70.2359	$70.24	$70.25	$70.20
Purchase #3	$59.67	12.866%	$67.3471	$67.35	$67.35	$67.30
Purchase #4	$27.33	12.543%	$30.758	$30.76	$30.75	$30.80
Purchase #5	$77.38	13.654%	$87.9455	$87.95	$87.95	$87.90
Purchase #6	$73.53	6.225%	$78.1072	$78.11	$78.10	$78.10
Purchase #7	$89.98	6.302%	$95.6505	$95.65	$95.65	$95.70
7 purchase totals =	$420.33		$462.8715	$462.89	$462.90	$462.80