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	$113.87	11.833%	$127.3442	$127.34	$127.35	$127.30
Purchase #2	$211.43	4.425%	$220.7858	$220.79	$220.80	$220.80
Purchase #3	$189.70	6.816%	$202.63	$202.63	$202.65	$202.60
Purchase #4	$214.30	8.410%	$232.3226	$232.32	$232.30	$232.30
Purchase #5	$61.47	4.618%	$64.3087	$64.31	$64.30	$64.30
Purchase #6	$131.64	10.186%	$145.0489	$145.05	$145.05	$145.00
Purchase #7	$80.59	12.373%	$90.5614	$90.56	$90.55	$90.60
7 purchase totals =	$1,003.00		$1,083.0016	$1,083.00	$1,083.00	$1,082.90