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	$12.94	4.870%	$13.5702	$13.57	$13.55	$13.60
Purchase #2	$47.73	11.589%	$53.2614	$53.26	$53.25	$53.30
Purchase #3	$14.79	4.758%	$15.4937	$15.49	$15.50	$15.50
Purchase #4	$8.82	8.424%	$9.563	$9.56	$9.55	$9.60
Purchase #5	$5.96	5.121%	$6.2652	$6.27	$6.25	$6.30
Purchase #6	$172.32	7.737%	$185.6524	$185.65	$185.65	$185.70
Purchase #7	$135.27	11.181%	$150.3945	$150.39	$150.40	$150.40
7 purchase totals =	$397.83		$434.2004	$434.19	$434.15	$434.40