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	$148.72	10.847%	$164.8517	$164.85	$164.85	$164.90
Purchase #2	$170.79	11.406%	$190.2703	$190.27	$190.25	$190.30
Purchase #3	$157.58	6.688%	$168.119	$168.12	$168.10	$168.10
Purchase #4	$129.90	11.130%	$144.3579	$144.36	$144.35	$144.40
Purchase #5	$175.83	8.320%	$190.4591	$190.46	$190.45	$190.50
Purchase #6	$249.43	8.224%	$269.9431	$269.94	$269.95	$269.90
Purchase #7	$58.40	6.219%	$62.0319	$62.03	$62.05	$62.00
7 purchase totals =	$1,090.65		$1,190.0330	$1,190.03	$1,190.00	$1,190.10