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	$78.73	4.796%	$82.5059	$82.51	$82.50	$82.50
Purchase #2	$89.55	6.713%	$95.5615	$95.56	$95.55	$95.60
Purchase #3	$162.27	13.471%	$184.1294	$184.13	$184.15	$184.10
Purchase #4	$211.84	4.191%	$220.7182	$220.72	$220.70	$220.70
Purchase #5	$185.80	13.388%	$210.6749	$210.67	$210.65	$210.70
Purchase #6	$125.44	13.400%	$142.249	$142.25	$142.25	$142.20
Purchase #7	$6.45	9.212%	$7.0442	$7.04	$7.05	$7.00
7 purchase totals =	$860.08		$942.8831	$942.88	$942.85	$942.80