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	$142.93	6.568%	$152.3176	$152.32	$152.30	$152.30
Purchase #2	$35.98	11.321%	$40.0533	$40.05	$40.05	$40.10
Purchase #3	$51.94	9.540%	$56.8951	$56.90	$56.90	$56.90
Purchase #4	$210.64	10.656%	$233.0858	$233.09	$233.10	$233.10
Purchase #5	$77.75	11.154%	$86.4222	$86.42	$86.40	$86.40
Purchase #6	$24.76	6.565%	$26.3855	$26.39	$26.40	$26.40
Purchase #7	$159.78	7.831%	$172.2924	$172.29	$172.30	$172.30
7 purchase totals =	$703.78		$767.4519	$767.46	$767.45	$767.50