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	$50.84	8.641%	$55.2331	$55.23	$55.25	$55.20
Purchase #2	$87.91	7.310%	$94.3362	$94.34	$94.35	$94.30
Purchase #3	$184.55	8.743%	$200.6852	$200.69	$200.70	$200.70
Purchase #4	$85.42	4.637%	$89.3809	$89.38	$89.40	$89.40
Purchase #5	$203.53	9.595%	$223.0587	$223.06	$223.05	$223.10
Purchase #6	$245.53	5.133%	$258.1331	$258.13	$258.15	$258.10
Purchase #7	$231.89	7.842%	$250.0748	$250.07	$250.05	$250.10
7 purchase totals =	$1,089.67		$1,170.9020	$1,170.90	$1,170.95	$1,170.90