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	$86.91	6.173%	$92.275	$92.28	$92.30	$92.30
Purchase #2	$152.78	6.240%	$162.3135	$162.31	$162.30	$162.30
Purchase #3	$67.55	7.278%	$72.4663	$72.47	$72.45	$72.50
Purchase #4	$42.90	5.709%	$45.3492	$45.35	$45.35	$45.30
Purchase #5	$187.95	4.672%	$196.731	$196.73	$196.75	$196.70
Purchase #6	$196.76	9.606%	$215.6608	$215.66	$215.65	$215.70
Purchase #7	$187.47	11.873%	$209.7283	$209.73	$209.75	$209.70
7 purchase totals =	$922.32		$994.5241	$994.53	$994.55	$994.50