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	$39.59	3.415%	$40.942	$40.94	$40.95	$40.90
Purchase #2	$83.87	10.314%	$92.5204	$92.52	$92.50	$92.50
Purchase #3	$206.73	6.444%	$220.0517	$220.05	$220.05	$220.10
Purchase #4	$191.63	7.204%	$205.435	$205.44	$205.45	$205.40
Purchase #5	$130.88	11.283%	$145.6472	$145.65	$145.65	$145.60
Purchase #6	$179.42	6.174%	$190.4974	$190.50	$190.50	$190.50
Purchase #7	$139.67	7.625%	$150.3198	$150.32	$150.30	$150.30
7 purchase totals =	$971.79		$1,045.4135	$1,045.42	$1,045.40	$1,045.30