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	$34.25	9.338%	$37.4483	$37.45	$37.45	$37.40
Purchase #2	$66.42	4.271%	$69.2568	$69.26	$69.25	$69.30
Purchase #3	$79.41	8.483%	$86.1464	$86.15	$86.15	$86.10
Purchase #4	$94.51	13.109%	$106.8993	$106.90	$106.90	$106.90
Purchase #5	$111.63	7.609%	$120.1239	$120.12	$120.10	$120.10
Purchase #6	$143.37	5.418%	$151.1378	$151.14	$151.15	$151.10
Purchase #7	$89.71	7.524%	$96.4598	$96.46	$96.45	$96.50
7 purchase totals =	$619.30		$667.4723	$667.48	$667.45	$667.40