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	$106.38	5.415%	$112.1405	$112.14	$112.15	$112.10
Purchase #2	$87.45	12.534%	$98.411	$98.41	$98.40	$98.40
Purchase #3	$145.56	5.258%	$153.2135	$153.21	$153.20	$153.20
Purchase #4	$231.94	13.644%	$263.5859	$263.59	$263.60	$263.60
Purchase #5	$238.53	12.575%	$268.5251	$268.53	$268.55	$268.50
Purchase #6	$83.46	8.425%	$90.4915	$90.49	$90.50	$90.50
Purchase #7	$131.54	7.277%	$141.1122	$141.11	$141.10	$141.10
7 purchase totals =	$1,024.86		$1,127.4797	$1,127.48	$1,127.50	$1,127.40