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	$60.38	5.602%	$63.7625	$63.76	$63.75	$63.80
Purchase #2	$234.74	11.375%	$261.4417	$261.44	$261.45	$261.40
Purchase #3	$54.78	9.316%	$59.8833	$59.88	$59.90	$59.90
Purchase #4	$98.62	10.694%	$109.1664	$109.17	$109.15	$109.20
Purchase #5	$169.77	9.341%	$185.6282	$185.63	$185.65	$185.60
Purchase #6	$159.76	13.538%	$181.3883	$181.39	$181.40	$181.40
Purchase #7	$168.45	9.603%	$184.6263	$184.63	$184.65	$184.60
7 purchase totals =	$946.50		$1,045.8967	$1,045.90	$1,045.95	$1,045.90