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	$212.89	7.594%	$229.0569	$229.06	$229.05	$229.10
Purchase #2	$109.82	8.802%	$119.4864	$119.49	$119.50	$119.50
Purchase #3	$59.29	3.605%	$61.4274	$61.43	$61.45	$61.40
Purchase #4	$23.91	8.301%	$25.8948	$25.89	$25.90	$25.90
Purchase #5	$104.54	3.637%	$108.3421	$108.34	$108.35	$108.30
Purchase #6	$195.48	7.192%	$209.5389	$209.54	$209.55	$209.50
Purchase #7	$27.96	8.552%	$30.3511	$30.35	$30.35	$30.40
7 purchase totals =	$733.89		$784.0976	$784.10	$784.15	$784.10