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	$233.92	4.856%	$245.2792	$245.28	$245.30	$245.30
Purchase #2	$77.89	6.591%	$83.0237	$83.02	$83.00	$83.00
Purchase #3	$161.27	8.385%	$174.7925	$174.79	$174.80	$174.80
Purchase #4	$45.77	10.241%	$50.4573	$50.46	$50.45	$50.50
Purchase #5	$139.93	9.441%	$153.1408	$153.14	$153.15	$153.10
Purchase #6	$96.26	3.261%	$99.399	$99.40	$99.40	$99.40
Purchase #7	$178.59	10.442%	$197.2384	$197.24	$197.25	$197.20
7 purchase totals =	$933.63		$1,003.3309	$1,003.33	$1,003.35	$1,003.30