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	$53.28	9.411%	$58.2942	$58.29	$58.30	$58.30
Purchase #2	$244.31	12.284%	$274.321	$274.32	$274.30	$274.30
Purchase #3	$101.38	3.322%	$104.7478	$104.75	$104.75	$104.70
Purchase #4	$235.45	7.516%	$253.1464	$253.15	$253.15	$253.10
Purchase #5	$53.89	9.709%	$59.1222	$59.12	$59.10	$59.10
Purchase #6	$72.27	8.350%	$78.3045	$78.30	$78.30	$78.30
Purchase #7	$182.37	10.523%	$201.5608	$201.56	$201.55	$201.60
7 purchase totals =	$942.95		$1,029.4969	$1,029.49	$1,029.45	$1,029.40