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	$162.91	6.641%	$173.7289	$173.73	$173.75	$173.70
Purchase #2	$204.62	9.581%	$224.2246	$224.22	$224.20	$224.20
Purchase #3	$78.53	13.457%	$89.0978	$89.10	$89.10	$89.10
Purchase #4	$50.97	6.598%	$54.333	$54.33	$54.35	$54.30
Purchase #5	$50.90	8.864%	$55.4118	$55.41	$55.40	$55.40
Purchase #6	$58.91	7.869%	$63.5456	$63.55	$63.55	$63.50
Purchase #7	$95.36	5.273%	$100.3883	$100.39	$100.40	$100.40
7 purchase totals =	$702.20		$760.7300	$760.73	$760.75	$760.60