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	$190.28	10.440%	$210.1452	$210.15	$210.15	$210.10
Purchase #2	$87.64	7.822%	$94.4952	$94.50	$94.50	$94.50
Purchase #3	$55.29	11.588%	$61.697	$61.70	$61.70	$61.70
Purchase #4	$73.87	11.798%	$82.5852	$82.59	$82.60	$82.60
Purchase #5	$56.62	3.649%	$58.6861	$58.69	$58.70	$58.70
Purchase #6	$33.41	11.435%	$37.2304	$37.23	$37.25	$37.20
Purchase #7	$175.40	4.604%	$183.4754	$183.48	$183.50	$183.50
7 purchase totals =	$672.51		$728.3145	$728.34	$728.40	$728.30