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	$145.32	4.863%	$152.3869	$152.39	$152.40	$152.40
Purchase #2	$223.52	3.491%	$231.3231	$231.32	$231.30	$231.30
Purchase #3	$70.99	13.269%	$80.4097	$80.41	$80.40	$80.40
Purchase #4	$174.45	9.398%	$190.8448	$190.84	$190.85	$190.80
Purchase #5	$42.93	10.550%	$47.4591	$47.46	$47.45	$47.50
Purchase #6	$179.44	7.230%	$192.4135	$192.41	$192.40	$192.40
Purchase #7	$231.96	9.380%	$253.7178	$253.72	$253.70	$253.70
7 purchase totals =	$1,068.61		$1,148.5549	$1,148.55	$1,148.50	$1,148.50