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	$166.64	4.542%	$174.2088	$174.21	$174.20	$174.20
Purchase #2	$93.97	11.132%	$104.4307	$104.43	$104.45	$104.40
Purchase #3	$160.61	9.586%	$176.0061	$176.01	$176.00	$176.00
Purchase #4	$74.90	9.288%	$81.8567	$81.86	$81.85	$81.90
Purchase #5	$124.89	9.859%	$137.2029	$137.20	$137.20	$137.20
Purchase #6	$245.75	3.102%	$253.3732	$253.37	$253.35	$253.40
Purchase #7	$83.27	7.556%	$89.5619	$89.56	$89.55	$89.60
7 purchase totals =	$950.03		$1,016.6403	$1,016.64	$1,016.60	$1,016.70