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	$113.90	4.599%	$119.1383	$119.14	$119.15	$119.10
Purchase #2	$33.35	7.445%	$35.8329	$35.83	$35.85	$35.80
Purchase #3	$146.97	7.670%	$158.2426	$158.24	$158.25	$158.20
Purchase #4	$216.81	7.719%	$233.5456	$233.55	$233.55	$233.50
Purchase #5	$179.28	3.488%	$185.5333	$185.53	$185.55	$185.50
Purchase #6	$69.36	3.856%	$72.0345	$72.03	$72.05	$72.00
Purchase #7	$221.33	12.641%	$249.3083	$249.31	$249.30	$249.30
7 purchase totals =	$981.00		$1,053.6355	$1,053.63	$1,053.70	$1,053.40