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	$13.41	6.755%	$14.3158	$14.32	$14.30	$14.30
Purchase #2	$177.91	10.543%	$196.6671	$196.67	$196.65	$196.70
Purchase #3	$68.67	4.679%	$71.8831	$71.88	$71.90	$71.90
Purchase #4	$178.58	7.315%	$191.6431	$191.64	$191.65	$191.60
Purchase #5	$91.61	4.608%	$95.8314	$95.83	$95.85	$95.80
Purchase #6	$160.63	4.637%	$168.0784	$168.08	$168.10	$168.10
Purchase #7	$72.65	9.673%	$79.6774	$79.68	$79.70	$79.70
7 purchase totals =	$763.46		$818.0963	$818.10	$818.15	$818.10