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	$79.42	7.324%	$85.2367	$85.24	$85.25	$85.20
Purchase #2	$159.28	7.849%	$171.7819	$171.78	$171.80	$171.80
Purchase #3	$100.65	5.360%	$106.0448	$106.04	$106.05	$106.00
Purchase #4	$185.58	3.655%	$192.3629	$192.36	$192.35	$192.40
Purchase #5	$166.52	10.103%	$183.3435	$183.34	$183.35	$183.30
Purchase #6	$109.44	12.542%	$123.166	$123.17	$123.15	$123.20
Purchase #7	$142.90	10.767%	$158.286	$158.29	$158.30	$158.30
7 purchase totals =	$943.79		$1,020.2218	$1,020.22	$1,020.25	$1,020.20