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	$227.79	4.194%	$237.3435	$237.34	$237.35	$237.30
Purchase #2	$159.73	13.643%	$181.522	$181.52	$181.50	$181.50
Purchase #3	$127.27	3.641%	$131.9039	$131.90	$131.90	$131.90
Purchase #4	$86.43	9.490%	$94.6322	$94.63	$94.65	$94.60
Purchase #5	$107.30	5.804%	$113.5277	$113.53	$113.55	$113.50
Purchase #6	$65.66	10.827%	$72.769	$72.77	$72.75	$72.80
Purchase #7	$176.26	5.148%	$185.3339	$185.33	$185.35	$185.30
7 purchase totals =	$950.44		$1,017.0322	$1,017.02	$1,017.05	$1,016.90