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	$182.98	12.612%	$206.0574	$206.06	$206.05	$206.10
Purchase #2	$165.99	3.658%	$172.0619	$172.06	$172.05	$172.10
Purchase #3	$247.88	8.375%	$268.64	$268.64	$268.65	$268.60
Purchase #4	$68.36	11.795%	$76.4231	$76.42	$76.40	$76.40
Purchase #5	$55.43	7.232%	$59.4387	$59.44	$59.45	$59.40
Purchase #6	$197.27	13.363%	$223.6312	$223.63	$223.65	$223.60
Purchase #7	$90.36	10.844%	$100.1586	$100.16	$100.15	$100.20
7 purchase totals =	$1,008.27		$1,106.4109	$1,106.41	$1,106.40	$1,106.40