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	$114.54	5.672%	$121.0367	$121.04	$121.05	$121.00
Purchase #2	$12.28	6.211%	$13.0427	$13.04	$13.05	$13.00
Purchase #3	$128.93	9.392%	$141.0391	$141.04	$141.05	$141.00
Purchase #4	$57.47	3.142%	$59.2757	$59.28	$59.30	$59.30
Purchase #5	$154.89	9.453%	$169.5318	$169.53	$169.55	$169.50
Purchase #6	$10.88	4.305%	$11.3484	$11.35	$11.35	$11.30
Purchase #7	$181.61	4.297%	$189.4138	$189.41	$189.40	$189.40
7 purchase totals =	$660.60		$704.6882	$704.69	$704.75	$704.50