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	$11.88	3.407%	$12.2848	$12.28	$12.30	$12.30
Purchase #2	$27.38	10.611%	$30.2853	$30.29	$30.30	$30.30
Purchase #3	$186.32	7.713%	$200.6909	$200.69	$200.70	$200.70
Purchase #4	$152.46	10.399%	$168.3143	$168.31	$168.30	$168.30
Purchase #5	$86.55	8.603%	$93.9959	$94.00	$94.00	$94.00
Purchase #6	$236.75	13.312%	$268.2662	$268.27	$268.25	$268.30
Purchase #7	$224.32	4.127%	$233.5777	$233.58	$233.60	$233.60
7 purchase totals =	$925.66		$1,007.4151	$1,007.42	$1,007.45	$1,007.50