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	$192.50	9.516%	$210.8183	$210.82	$210.80	$210.80
Purchase #2	$53.36	5.654%	$56.377	$56.38	$56.40	$56.40
Purchase #3	$6.42	4.753%	$6.7251	$6.73	$6.75	$6.70
Purchase #4	$108.75	3.210%	$112.2409	$112.24	$112.25	$112.20
Purchase #5	$233.53	13.196%	$264.3466	$264.35	$264.35	$264.30
Purchase #6	$206.93	10.784%	$229.2453	$229.25	$229.25	$229.20
Purchase #7	$181.88	5.286%	$191.4942	$191.49	$191.50	$191.50
7 purchase totals =	$983.37		$1,071.2474	$1,071.26	$1,071.30	$1,071.10