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	$43.86	10.649%	$48.5307	$48.53	$48.55	$48.50
Purchase #2	$124.74	11.518%	$139.1076	$139.11	$139.10	$139.10
Purchase #3	$233.37	3.640%	$241.8647	$241.86	$241.85	$241.90
Purchase #4	$109.44	13.111%	$123.7887	$123.79	$123.80	$123.80
Purchase #5	$139.75	11.757%	$156.1804	$156.18	$156.20	$156.20
Purchase #6	$211.35	13.599%	$240.0915	$240.09	$240.10	$240.10
Purchase #7	$65.37	7.696%	$70.4009	$70.40	$70.40	$70.40
7 purchase totals =	$927.88		$1,019.9645	$1,019.96	$1,020.00	$1,020.00