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	$161.78	12.346%	$181.7534	$181.75	$181.75	$181.80
Purchase #2	$172.77	7.522%	$185.7658	$185.77	$185.75	$185.80
Purchase #3	$41.84	11.114%	$46.4901	$46.49	$46.50	$46.50
Purchase #4	$122.83	11.113%	$136.4801	$136.48	$136.50	$136.50
Purchase #5	$218.97	11.521%	$244.1975	$244.20	$244.20	$244.20
Purchase #6	$43.74	6.828%	$46.7266	$46.73	$46.75	$46.70
Purchase #7	$164.63	12.476%	$185.1692	$185.17	$185.15	$185.20
7 purchase totals =	$926.56		$1,026.5827	$1,026.59	$1,026.60	$1,026.70