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	$98.40	3.705%	$102.0457	$102.05	$102.05	$102.00
Purchase #2	$135.61	12.196%	$152.149	$152.15	$152.15	$152.10
Purchase #3	$123.53	13.598%	$140.3276	$140.33	$140.35	$140.30
Purchase #4	$233.42	4.624%	$244.2133	$244.21	$244.20	$244.20
Purchase #5	$69.94	13.363%	$79.2861	$79.29	$79.30	$79.30
Purchase #6	$221.89	12.823%	$250.343	$250.34	$250.35	$250.30
Purchase #7	$59.39	5.156%	$62.4521	$62.45	$62.45	$62.50
7 purchase totals =	$942.18		$1,030.8168	$1,030.82	$1,030.85	$1,030.70