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	$122.43	7.762%	$131.933	$131.93	$131.95	$131.90
Purchase #2	$172.81	13.738%	$196.5506	$196.55	$196.55	$196.60
Purchase #3	$151.48	7.188%	$162.3684	$162.37	$162.35	$162.40
Purchase #4	$102.33	6.369%	$108.8474	$108.85	$108.85	$108.80
Purchase #5	$239.86	9.522%	$262.6995	$262.70	$262.70	$262.70
Purchase #6	$93.93	5.170%	$98.7862	$98.79	$98.80	$98.80
Purchase #7	$89.91	7.721%	$96.852	$96.85	$96.85	$96.90
7 purchase totals =	$972.75		$1,058.0371	$1,058.04	$1,058.05	$1,058.10