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	$173.36	13.512%	$196.7844	$196.78	$196.80	$196.80
Purchase #2	$53.84	9.784%	$59.1077	$59.11	$59.10	$59.10
Purchase #3	$69.64	10.853%	$77.198	$77.20	$77.20	$77.20
Purchase #4	$202.31	4.510%	$211.4342	$211.43	$211.45	$211.40
Purchase #5	$211.42	13.763%	$240.5177	$240.52	$240.50	$240.50
Purchase #6	$110.52	12.288%	$124.1007	$124.10	$124.10	$124.10
Purchase #7	$121.80	11.657%	$135.9982	$136.00	$136.00	$136.00
7 purchase totals =	$942.89		$1,045.1409	$1,045.14	$1,045.15	$1,045.10