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	$165.69	11.339%	$184.4776	$184.48	$184.50	$184.50
Purchase #2	$73.67	4.140%	$76.7199	$76.72	$76.70	$76.70
Purchase #3	$247.69	6.838%	$264.627	$264.63	$264.65	$264.60
Purchase #4	$148.87	7.841%	$160.5429	$160.54	$160.55	$160.50
Purchase #5	$229.48	3.455%	$237.4085	$237.41	$237.40	$237.40
Purchase #6	$55.81	4.527%	$58.3365	$58.34	$58.35	$58.30
Purchase #7	$187.81	6.718%	$200.4271	$200.43	$200.45	$200.40
7 purchase totals =	$1,109.02		$1,182.5395	$1,182.55	$1,182.60	$1,182.40