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	$76.76	7.616%	$82.606	$82.61	$82.60	$82.60
Purchase #2	$11.87	12.540%	$13.3585	$13.36	$13.35	$13.40
Purchase #3	$249.47	8.139%	$269.7744	$269.77	$269.75	$269.80
Purchase #4	$49.89	6.608%	$53.1867	$53.19	$53.20	$53.20
Purchase #5	$226.39	8.181%	$244.911	$244.91	$244.90	$244.90
Purchase #6	$89.92	7.133%	$96.334	$96.33	$96.35	$96.30
Purchase #7	$30.59	7.355%	$32.8399	$32.84	$32.85	$32.80
7 purchase totals =	$734.89		$793.0105	$793.01	$793.00	$793.00