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	$216.70	5.305%	$228.1959	$228.20	$228.20	$228.20
Purchase #2	$72.72	13.161%	$82.2907	$82.29	$82.30	$82.30
Purchase #3	$53.57	3.674%	$55.5382	$55.54	$55.55	$55.50
Purchase #4	$141.42	10.137%	$155.7557	$155.76	$155.75	$155.80
Purchase #5	$25.44	10.170%	$28.0272	$28.03	$28.05	$28.00
Purchase #6	$54.38	10.129%	$59.8882	$59.89	$59.90	$59.90
Purchase #7	$5.75	10.456%	$6.3512	$6.35	$6.35	$6.40
7 purchase totals =	$569.98		$616.0471	$616.06	$616.10	$616.10