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	$155.71	5.871%	$164.8517	$164.85	$164.85	$164.90
Purchase #2	$55.40	3.197%	$57.1711	$57.17	$57.15	$57.20
Purchase #3	$21.66	13.512%	$24.5867	$24.59	$24.60	$24.60
Purchase #4	$69.28	4.408%	$72.3339	$72.33	$72.35	$72.30
Purchase #5	$31.96	8.824%	$34.7802	$34.78	$34.80	$34.80
Purchase #6	$79.91	6.692%	$85.2576	$85.26	$85.25	$85.30
Purchase #7	$43.26	5.259%	$45.535	$45.54	$45.55	$45.50
7 purchase totals =	$457.18		$484.5162	$484.52	$484.55	$484.60