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	$239.59	10.379%	$264.457	$264.46	$264.45	$264.50
Purchase #2	$73.77	8.539%	$80.0692	$80.07	$80.05	$80.10
Purchase #3	$148.87	11.683%	$166.2625	$166.26	$166.25	$166.30
Purchase #4	$222.92	9.441%	$243.9659	$243.97	$243.95	$244.00
Purchase #5	$181.95	4.746%	$190.5853	$190.59	$190.60	$190.60
Purchase #6	$42.68	6.501%	$45.4546	$45.45	$45.45	$45.50
Purchase #7	$140.70	9.529%	$154.1073	$154.11	$154.10	$154.10
7 purchase totals =	$1,050.48		$1,144.9018	$1,144.91	$1,144.85	$1,145.10