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	$144.28	12.302%	$162.0293	$162.03	$162.05	$162.00
Purchase #2	$168.52	6.523%	$179.5126	$179.51	$179.50	$179.50
Purchase #3	$135.71	12.495%	$152.667	$152.67	$152.65	$152.70
Purchase #4	$152.41	12.360%	$171.2479	$171.25	$171.25	$171.20
Purchase #5	$86.81	11.812%	$97.064	$97.06	$97.05	$97.10
Purchase #6	$121.71	7.493%	$130.8297	$130.83	$130.85	$130.80
Purchase #7	$238.95	4.802%	$250.4244	$250.42	$250.40	$250.40
7 purchase totals =	$1,048.39		$1,143.7749	$1,143.77	$1,143.75	$1,143.70