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	$68.74	5.188%	$72.3062	$72.31	$72.30	$72.30
Purchase #2	$6.36	7.559%	$6.8408	$6.84	$6.85	$6.80
Purchase #3	$91.75	5.458%	$96.7577	$96.76	$96.75	$96.80
Purchase #4	$248.77	10.367%	$274.56	$274.56	$274.55	$274.60
Purchase #5	$209.87	13.538%	$238.2822	$238.28	$238.30	$238.30
Purchase #6	$133.86	3.447%	$138.4742	$138.47	$138.45	$138.50
Purchase #7	$208.95	6.781%	$223.1189	$223.12	$223.10	$223.10
7 purchase totals =	$968.30		$1,050.3400	$1,050.34	$1,050.30	$1,050.40