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	$85.27	13.317%	$96.6254	$96.63	$96.65	$96.60
Purchase #2	$109.98	12.379%	$123.5944	$123.59	$123.60	$123.60
Purchase #3	$64.68	13.367%	$73.3258	$73.33	$73.35	$73.30
Purchase #4	$127.58	9.172%	$139.2816	$139.28	$139.30	$139.30
Purchase #5	$135.59	11.490%	$151.1693	$151.17	$151.15	$151.20
Purchase #6	$154.45	3.825%	$160.3577	$160.36	$160.35	$160.40
Purchase #7	$43.31	11.151%	$48.1395	$48.14	$48.15	$48.10
7 purchase totals =	$720.86		$792.4937	$792.50	$792.55	$792.50