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	$62.33	11.198%	$69.3097	$69.31	$69.30	$69.30
Purchase #2	$64.59	11.250%	$71.8564	$71.86	$71.85	$71.90
Purchase #3	$59.87	4.463%	$62.542	$62.54	$62.55	$62.50
Purchase #4	$124.96	13.118%	$141.3523	$141.35	$141.35	$141.40
Purchase #5	$225.90	12.836%	$254.8965	$254.90	$254.90	$254.90
Purchase #6	$79.96	13.460%	$90.7226	$90.72	$90.70	$90.70
Purchase #7	$36.79	3.626%	$38.124	$38.12	$38.10	$38.10
7 purchase totals =	$654.40		$728.8035	$728.80	$728.75	$728.80