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	$50.81	8.661%	$55.2107	$55.21	$55.20	$55.20
Purchase #2	$205.27	5.246%	$216.0385	$216.04	$216.05	$216.00
Purchase #3	$136.85	9.119%	$149.3294	$149.33	$149.35	$149.30
Purchase #4	$231.94	9.245%	$253.3829	$253.38	$253.40	$253.40
Purchase #5	$240.77	11.498%	$268.4537	$268.45	$268.45	$268.50
Purchase #6	$192.40	9.388%	$210.4625	$210.46	$210.45	$210.50
Purchase #7	$94.86	11.284%	$105.564	$105.56	$105.55	$105.60
7 purchase totals =	$1,152.90		$1,258.4417	$1,258.43	$1,258.45	$1,258.50