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	$86.30	5.292%	$90.867	$90.87	$90.85	$90.90
Purchase #2	$114.79	10.740%	$127.1184	$127.12	$127.10	$127.10
Purchase #3	$72.38	5.731%	$76.5281	$76.53	$76.55	$76.50
Purchase #4	$135.88	8.104%	$146.8917	$146.89	$146.90	$146.90
Purchase #5	$192.27	6.581%	$204.9233	$204.92	$204.90	$204.90
Purchase #6	$187.63	11.502%	$209.2112	$209.21	$209.20	$209.20
Purchase #7	$186.88	4.675%	$195.6166	$195.62	$195.60	$195.60
7 purchase totals =	$976.13		$1,051.1563	$1,051.16	$1,051.10	$1,051.10