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	$227.47	12.600%	$256.1312	$256.13	$256.15	$256.10
Purchase #2	$36.46	4.320%	$38.0351	$38.04	$38.05	$38.00
Purchase #3	$67.43	4.659%	$70.5716	$70.57	$70.55	$70.60
Purchase #4	$191.46	6.739%	$204.3625	$204.36	$204.35	$204.40
Purchase #5	$104.55	4.420%	$109.1711	$109.17	$109.15	$109.20
Purchase #6	$216.53	4.476%	$226.2219	$226.22	$226.20	$226.20
Purchase #7	$220.86	8.850%	$240.4061	$240.41	$240.40	$240.40
7 purchase totals =	$1,064.76		$1,144.8995	$1,144.90	$1,144.85	$1,144.90