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	$178.88	3.488%	$185.1193	$185.12	$185.10	$185.10
Purchase #2	$104.94	5.276%	$110.4766	$110.48	$110.50	$110.50
Purchase #3	$128.50	8.645%	$139.6088	$139.61	$139.60	$139.60
Purchase #4	$190.74	4.807%	$199.9089	$199.91	$199.90	$199.90
Purchase #5	$127.73	13.653%	$145.169	$145.17	$145.15	$145.20
Purchase #6	$151.65	5.573%	$160.1015	$160.10	$160.10	$160.10
Purchase #7	$142.39	8.247%	$154.1329	$154.13	$154.15	$154.10
7 purchase totals =	$1,024.83		$1,094.5170	$1,094.52	$1,094.50	$1,094.50