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	$27.40	4.215%	$28.5549	$28.55	$28.55	$28.60
Purchase #2	$230.55	4.662%	$241.2982	$241.30	$241.30	$241.30
Purchase #3	$137.56	3.501%	$142.376	$142.38	$142.40	$142.40
Purchase #4	$234.71	6.473%	$249.9028	$249.90	$249.90	$249.90
Purchase #5	$133.52	12.708%	$150.4877	$150.49	$150.50	$150.50
Purchase #6	$64.73	4.172%	$67.4305	$67.43	$67.45	$67.40
Purchase #7	$244.54	11.570%	$272.8333	$272.83	$272.85	$272.80
7 purchase totals =	$1,073.01		$1,152.8834	$1,152.88	$1,152.95	$1,152.90