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	$13.32	10.619%	$14.7345	$14.73	$14.75	$14.70
Purchase #2	$162.77	13.829%	$185.2795	$185.28	$185.30	$185.30
Purchase #3	$239.32	10.427%	$264.2739	$264.27	$264.25	$264.30
Purchase #4	$192.90	12.370%	$216.7617	$216.76	$216.75	$216.80
Purchase #5	$169.79	11.243%	$188.8795	$188.88	$188.90	$188.90
Purchase #6	$73.78	8.370%	$79.9554	$79.96	$79.95	$80.00
Purchase #7	$193.88	12.717%	$218.5357	$218.54	$218.55	$218.50
7 purchase totals =	$1,045.76		$1,168.4202	$1,168.42	$1,168.45	$1,168.50