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	$167.79	3.713%	$174.02	$174.02	$174.00	$174.00
Purchase #2	$232.83	4.133%	$242.4529	$242.45	$242.45	$242.50
Purchase #3	$244.75	7.652%	$263.4783	$263.48	$263.50	$263.50
Purchase #4	$33.96	10.460%	$37.5122	$37.51	$37.50	$37.50
Purchase #5	$130.95	10.127%	$144.2113	$144.21	$144.20	$144.20
Purchase #6	$74.65	11.476%	$83.2168	$83.22	$83.20	$83.20
Purchase #7	$73.42	12.286%	$82.4404	$82.44	$82.45	$82.40
7 purchase totals =	$958.35		$1,027.3319	$1,027.33	$1,027.30	$1,027.30