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	$67.32	10.667%	$74.501	$74.50	$74.50	$74.50
Purchase #2	$152.77	12.442%	$171.7776	$171.78	$171.80	$171.80
Purchase #3	$202.74	4.272%	$211.4011	$211.40	$211.40	$211.40
Purchase #4	$227.35	10.364%	$250.9126	$250.91	$250.90	$250.90
Purchase #5	$195.33	10.356%	$215.5584	$215.56	$215.55	$215.60
Purchase #6	$65.84	11.744%	$73.5722	$73.57	$73.55	$73.60
Purchase #7	$133.80	6.449%	$142.4288	$142.43	$142.45	$142.40
7 purchase totals =	$1,045.15		$1,140.1517	$1,140.15	$1,140.15	$1,140.20