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	$114.69	9.317%	$125.3757	$125.38	$125.40	$125.40
Purchase #2	$168.43	11.713%	$188.1582	$188.16	$188.15	$188.20
Purchase #3	$101.54	8.654%	$110.3273	$110.33	$110.35	$110.30
Purchase #4	$57.82	9.480%	$63.3013	$63.30	$63.30	$63.30
Purchase #5	$237.45	7.418%	$255.064	$255.06	$255.05	$255.10
Purchase #6	$37.30	13.584%	$42.3668	$42.37	$42.35	$42.40
Purchase #7	$224.93	10.570%	$248.7051	$248.71	$248.70	$248.70
7 purchase totals =	$942.16		$1,033.2984	$1,033.31	$1,033.30	$1,033.40