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	$31.26	3.667%	$32.4063	$32.41	$32.40	$32.40
Purchase #2	$152.57	9.228%	$166.6492	$166.65	$166.65	$166.60
Purchase #3	$50.70	11.407%	$56.4833	$56.48	$56.50	$56.50
Purchase #4	$40.91	5.428%	$43.1306	$43.13	$43.15	$43.10
Purchase #5	$250.53	3.171%	$258.4743	$258.47	$258.45	$258.50
Purchase #6	$219.81	11.819%	$245.7893	$245.79	$245.80	$245.80
Purchase #7	$246.60	3.640%	$255.5762	$255.58	$255.60	$255.60
7 purchase totals =	$992.38		$1,058.5092	$1,058.51	$1,058.55	$1,058.50