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	$165.83	9.270%	$181.2024	$181.20	$181.20	$181.20
Purchase #2	$250.35	13.488%	$284.1172	$284.12	$284.10	$284.10
Purchase #3	$67.78	4.600%	$70.8979	$70.90	$70.90	$70.90
Purchase #4	$201.40	6.707%	$214.9079	$214.91	$214.90	$214.90
Purchase #5	$152.89	9.153%	$166.884	$166.88	$166.90	$166.90
Purchase #6	$43.73	10.737%	$48.4253	$48.43	$48.45	$48.40
Purchase #7	$162.53	13.129%	$183.8686	$183.87	$183.85	$183.90
7 purchase totals =	$1,044.51		$1,150.3033	$1,150.31	$1,150.30	$1,150.30