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	$70.97	7.695%	$76.4311	$76.43	$76.45	$76.40
Purchase #2	$76.33	8.523%	$82.8356	$82.84	$82.85	$82.80
Purchase #3	$250.31	5.834%	$264.9131	$264.91	$264.90	$264.90
Purchase #4	$101.29	5.409%	$106.7688	$106.77	$106.75	$106.80
Purchase #5	$164.45	12.590%	$185.1543	$185.15	$185.15	$185.20
Purchase #6	$164.73	12.828%	$185.8616	$185.86	$185.85	$185.90
Purchase #7	$141.77	6.378%	$150.8121	$150.81	$150.80	$150.80
7 purchase totals =	$969.85		$1,052.7766	$1,052.77	$1,052.75	$1,052.80