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	$211.71	5.251%	$222.8269	$222.83	$222.85	$222.80
Purchase #2	$80.97	11.423%	$90.2192	$90.22	$90.20	$90.20
Purchase #3	$94.59	6.869%	$101.0874	$101.09	$101.10	$101.10
Purchase #4	$48.92	11.474%	$54.5331	$54.53	$54.55	$54.50
Purchase #5	$103.75	8.268%	$112.3281	$112.33	$112.35	$112.30
Purchase #6	$157.73	4.691%	$165.1291	$165.13	$165.15	$165.10
Purchase #7	$26.48	3.633%	$27.442	$27.44	$27.45	$27.40
7 purchase totals =	$724.15		$773.5658	$773.57	$773.65	$773.40