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	$75.77	12.585%	$85.3057	$85.31	$85.30	$85.30
Purchase #2	$141.50	6.223%	$150.3055	$150.31	$150.30	$150.30
Purchase #3	$232.47	13.675%	$264.2603	$264.26	$264.25	$264.30
Purchase #4	$181.32	4.740%	$189.9146	$189.91	$189.90	$189.90
Purchase #5	$211.76	11.811%	$236.771	$236.77	$236.75	$236.80
Purchase #6	$248.81	10.279%	$274.3852	$274.39	$274.40	$274.40
Purchase #7	$127.97	13.650%	$145.4379	$145.44	$145.45	$145.40
7 purchase totals =	$1,219.60		$1,346.3802	$1,346.39	$1,346.35	$1,346.40