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	$105.69	5.552%	$111.5579	$111.56	$111.55	$111.60
Purchase #2	$86.52	3.404%	$89.4651	$89.47	$89.45	$89.50
Purchase #3	$206.42	10.150%	$227.3716	$227.37	$227.35	$227.40
Purchase #4	$144.84	9.543%	$158.6621	$158.66	$158.65	$158.70
Purchase #5	$136.28	12.202%	$152.9089	$152.91	$152.90	$152.90
Purchase #6	$96.69	10.159%	$106.5127	$106.51	$106.50	$106.50
Purchase #7	$190.40	13.319%	$215.7594	$215.76	$215.75	$215.80
7 purchase totals =	$966.84		$1,062.2377	$1,062.24	$1,062.15	$1,062.40