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	$134.48	13.361%	$152.4479	$152.45	$152.45	$152.40
Purchase #2	$111.64	10.268%	$123.1032	$123.10	$123.10	$123.10
Purchase #3	$86.84	10.630%	$96.0711	$96.07	$96.05	$96.10
Purchase #4	$147.30	5.515%	$155.4236	$155.42	$155.40	$155.40
Purchase #5	$59.35	11.829%	$66.3705	$66.37	$66.35	$66.40
Purchase #6	$90.36	10.791%	$100.1107	$100.11	$100.10	$100.10
Purchase #7	$102.47	4.801%	$107.3896	$107.39	$107.40	$107.40
7 purchase totals =	$732.44		$800.9166	$800.91	$800.85	$800.90