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	$88.61	3.661%	$91.854	$91.85	$91.85	$91.90
Purchase #2	$248.71	10.594%	$275.0583	$275.06	$275.05	$275.10
Purchase #3	$187.90	5.449%	$198.1387	$198.14	$198.15	$198.10
Purchase #4	$226.82	12.515%	$255.2065	$255.21	$255.20	$255.20
Purchase #5	$220.67	6.502%	$235.018	$235.02	$235.00	$235.00
Purchase #6	$90.86	10.195%	$100.1232	$100.12	$100.10	$100.10
Purchase #7	$241.89	3.366%	$250.032	$250.03	$250.05	$250.00
7 purchase totals =	$1,305.46		$1,405.4307	$1,405.43	$1,405.40	$1,405.40