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	$212.52	3.418%	$219.7839	$219.78	$219.80	$219.80
Purchase #2	$83.34	3.823%	$86.5261	$86.53	$86.55	$86.50
Purchase #3	$32.94	7.656%	$35.4619	$35.46	$35.45	$35.50
Purchase #4	$108.69	11.270%	$120.9394	$120.94	$120.95	$120.90
Purchase #5	$212.82	10.449%	$235.0576	$235.06	$235.05	$235.10
Purchase #6	$139.48	9.215%	$152.3331	$152.33	$152.35	$152.30
Purchase #7	$239.68	8.203%	$259.341	$259.34	$259.35	$259.30
7 purchase totals =	$1,029.47		$1,109.4430	$1,109.44	$1,109.50	$1,109.40