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	$40.48	11.738%	$45.2315	$45.23	$45.25	$45.20
Purchase #2	$104.88	13.205%	$118.7294	$118.73	$118.75	$118.70
Purchase #3	$244.37	6.510%	$260.2785	$260.28	$260.30	$260.30
Purchase #4	$82.92	7.871%	$89.4466	$89.45	$89.45	$89.40
Purchase #5	$249.33	10.781%	$276.2103	$276.21	$276.20	$276.20
Purchase #6	$143.26	11.824%	$160.1991	$160.20	$160.20	$160.20
Purchase #7	$103.86	4.407%	$108.4371	$108.44	$108.45	$108.40
7 purchase totals =	$969.10		$1,058.5325	$1,058.54	$1,058.60	$1,058.40