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	$161.46	11.336%	$179.7631	$179.76	$179.75	$179.80
Purchase #2	$37.35	13.253%	$42.3	$42.30	$42.30	$42.30
Purchase #3	$82.97	9.532%	$90.8787	$90.88	$90.90	$90.90
Purchase #4	$188.67	8.428%	$204.5711	$204.57	$204.55	$204.60
Purchase #5	$164.28	3.801%	$170.5243	$170.52	$170.50	$170.50
Purchase #6	$127.63	6.417%	$135.82	$135.82	$135.80	$135.80
Purchase #7	$35.87	4.121%	$37.3482	$37.35	$37.35	$37.30
7 purchase totals =	$798.23		$861.2054	$861.20	$861.15	$861.20