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	$59.61	4.205%	$62.1166	$62.12	$62.10	$62.10
Purchase #2	$33.30	5.415%	$35.1032	$35.10	$35.10	$35.10
Purchase #3	$248.94	4.415%	$259.9307	$259.93	$259.95	$259.90
Purchase #4	$120.98	9.337%	$132.2759	$132.28	$132.30	$132.30
Purchase #5	$100.85	3.758%	$104.6399	$104.64	$104.65	$104.60
Purchase #6	$136.34	7.774%	$146.9391	$146.94	$146.95	$146.90
Purchase #7	$72.31	5.839%	$76.5322	$76.53	$76.55	$76.50
7 purchase totals =	$772.33		$817.5376	$817.54	$817.60	$817.40