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	$147.82	11.656%	$165.0499	$165.05	$165.05	$165.00
Purchase #2	$50.48	8.767%	$54.9056	$54.91	$54.90	$54.90
Purchase #3	$60.89	5.788%	$64.4143	$64.41	$64.40	$64.40
Purchase #4	$165.88	5.808%	$175.5143	$175.51	$175.50	$175.50
Purchase #5	$181.87	6.183%	$193.115	$193.12	$193.10	$193.10
Purchase #6	$50.55	13.666%	$57.4582	$57.46	$57.45	$57.50
Purchase #7	$12.34	5.864%	$13.0636	$13.06	$13.05	$13.10
7 purchase totals =	$669.83		$723.5209	$723.52	$723.45	$723.50