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	$92.48	7.853%	$99.7425	$99.74	$99.75	$99.70
Purchase #2	$90.83	3.650%	$94.1453	$94.15	$94.15	$94.10
Purchase #3	$33.36	5.495%	$35.1931	$35.19	$35.20	$35.20
Purchase #4	$85.90	12.785%	$96.8823	$96.88	$96.90	$96.90
Purchase #5	$111.30	3.782%	$115.5094	$115.51	$115.50	$115.50
Purchase #6	$188.35	11.845%	$210.6601	$210.66	$210.65	$210.70
Purchase #7	$157.94	9.146%	$172.3852	$172.39	$172.40	$172.40
7 purchase totals =	$760.16		$824.5179	$824.52	$824.55	$824.50