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	$197.58	4.160%	$205.7993	$205.80	$205.80	$205.80
Purchase #2	$86.28	4.449%	$90.1186	$90.12	$90.10	$90.10
Purchase #3	$220.42	3.795%	$228.7849	$228.78	$228.80	$228.80
Purchase #4	$216.91	10.606%	$239.9155	$239.92	$239.90	$239.90
Purchase #5	$235.94	11.797%	$263.7738	$263.77	$263.75	$263.80
Purchase #6	$238.92	4.860%	$250.5315	$250.53	$250.55	$250.50
Purchase #7	$52.60	3.412%	$54.3947	$54.39	$54.40	$54.40
7 purchase totals =	$1,248.65		$1,333.3183	$1,333.31	$1,333.30	$1,333.30