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	$95.73	3.572%	$99.1495	$99.15	$99.15	$99.10
Purchase #2	$148.31	4.684%	$155.2568	$155.26	$155.25	$155.30
Purchase #3	$13.33	4.130%	$13.8805	$13.88	$13.90	$13.90
Purchase #4	$181.37	4.394%	$189.3394	$189.34	$189.35	$189.30
Purchase #5	$244.79	13.274%	$277.2834	$277.28	$277.30	$277.30
Purchase #6	$170.87	11.796%	$191.0258	$191.03	$191.05	$191.00
Purchase #7	$233.48	11.552%	$260.4516	$260.45	$260.45	$260.50
7 purchase totals =	$1,087.88		$1,186.3870	$1,186.39	$1,186.45	$1,186.40