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	$71.87	10.417%	$79.3567	$79.36	$79.35	$79.40
Purchase #2	$130.64	11.842%	$146.1104	$146.11	$146.10	$146.10
Purchase #3	$52.74	9.692%	$57.8516	$57.85	$57.85	$57.90
Purchase #4	$115.44	10.282%	$127.3095	$127.31	$127.30	$127.30
Purchase #5	$186.75	11.476%	$208.1814	$208.18	$208.20	$208.20
Purchase #6	$220.82	6.312%	$234.7582	$234.76	$234.75	$234.80
Purchase #7	$244.78	4.290%	$255.2811	$255.28	$255.30	$255.30
7 purchase totals =	$1,023.04		$1,108.8489	$1,108.85	$1,108.85	$1,109.00