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	$37.73	8.389%	$40.8952	$40.90	$40.90	$40.90
Purchase #2	$145.32	8.557%	$157.755	$157.76	$157.75	$157.80
Purchase #3	$198.49	5.666%	$209.7364	$209.74	$209.75	$209.70
Purchase #4	$119.52	5.611%	$126.2263	$126.23	$126.25	$126.20
Purchase #5	$160.72	7.405%	$172.6213	$172.62	$172.60	$172.60
Purchase #6	$249.48	7.449%	$268.0638	$268.06	$268.05	$268.10
Purchase #7	$31.63	12.555%	$35.6011	$35.60	$35.60	$35.60
7 purchase totals =	$942.89		$1,010.8991	$1,010.91	$1,010.90	$1,010.90