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	$171.69	3.758%	$178.1421	$178.14	$178.15	$178.10
Purchase #2	$142.53	7.227%	$152.8306	$152.83	$152.85	$152.80
Purchase #3	$26.94	9.489%	$29.4963	$29.50	$29.50	$29.50
Purchase #4	$160.76	11.402%	$179.0899	$179.09	$179.10	$179.10
Purchase #5	$165.52	5.510%	$174.6402	$174.64	$174.65	$174.60
Purchase #6	$227.55	7.222%	$243.9837	$243.98	$244.00	$244.00
Purchase #7	$184.83	5.378%	$194.7702	$194.77	$194.75	$194.80
7 purchase totals =	$1,079.82		$1,152.9530	$1,152.95	$1,153.00	$1,152.90