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	$59.35	5.766%	$62.7721	$62.77	$62.75	$62.80
Purchase #2	$46.70	6.187%	$49.5893	$49.59	$49.60	$49.60
Purchase #3	$93.49	3.608%	$96.8631	$96.86	$96.85	$96.90
Purchase #4	$190.68	7.812%	$205.5759	$205.58	$205.60	$205.60
Purchase #5	$231.78	9.487%	$253.769	$253.77	$253.75	$253.80
Purchase #6	$100.96	3.487%	$104.4805	$104.48	$104.50	$104.50
Purchase #7	$201.28	13.805%	$229.0667	$229.07	$229.05	$229.10
7 purchase totals =	$924.24		$1,002.1166	$1,002.12	$1,002.10	$1,002.30