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	$50.69	3.471%	$52.4494	$52.45	$52.45	$52.40
Purchase #2	$206.50	12.866%	$233.0683	$233.07	$233.05	$233.10
Purchase #3	$92.36	4.237%	$96.2733	$96.27	$96.25	$96.30
Purchase #4	$49.96	11.661%	$55.7858	$55.79	$55.80	$55.80
Purchase #5	$47.83	13.672%	$54.3693	$54.37	$54.35	$54.40
Purchase #6	$142.73	13.647%	$162.2084	$162.21	$162.20	$162.20
Purchase #7	$69.94	11.802%	$78.1943	$78.19	$78.20	$78.20
7 purchase totals =	$660.01		$732.3488	$732.35	$732.30	$732.40