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	$89.99	5.628%	$95.0546	$95.05	$95.05	$95.10
Purchase #2	$56.60	7.837%	$61.0357	$61.04	$61.05	$61.00
Purchase #3	$229.27	5.564%	$242.0266	$242.03	$242.05	$242.00
Purchase #4	$148.47	10.566%	$164.1573	$164.16	$164.15	$164.20
Purchase #5	$64.68	10.538%	$71.496	$71.50	$71.50	$71.50
Purchase #6	$50.61	9.335%	$55.3344	$55.33	$55.35	$55.30
Purchase #7	$53.36	10.616%	$59.0247	$59.02	$59.00	$59.00
7 purchase totals =	$692.98		$748.1293	$748.13	$748.15	$748.10