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	$101.85	12.231%	$114.3073	$114.31	$114.30	$114.30
Purchase #2	$250.65	10.218%	$276.2614	$276.26	$276.25	$276.30
Purchase #3	$141.63	7.747%	$152.6021	$152.60	$152.60	$152.60
Purchase #4	$188.84	6.328%	$200.7898	$200.79	$200.80	$200.80
Purchase #5	$19.75	5.234%	$20.7837	$20.78	$20.80	$20.80
Purchase #6	$29.48	11.316%	$32.816	$32.82	$32.80	$32.80
Purchase #7	$234.79	8.842%	$255.5501	$255.55	$255.55	$255.60
7 purchase totals =	$966.99		$1,053.1104	$1,053.11	$1,053.10	$1,053.20