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	$96.85	10.453%	$106.9737	$106.97	$106.95	$107.00
Purchase #2	$235.59	3.415%	$243.6354	$243.64	$243.65	$243.60
Purchase #3	$134.98	4.817%	$141.482	$141.48	$141.50	$141.50
Purchase #4	$47.92	9.391%	$52.4202	$52.42	$52.40	$52.40
Purchase #5	$172.30	4.503%	$180.0587	$180.06	$180.05	$180.10
Purchase #6	$165.93	11.507%	$185.0236	$185.02	$185.00	$185.00
Purchase #7	$65.38	11.316%	$72.7784	$72.78	$72.80	$72.80
7 purchase totals =	$918.95		$982.3720	$982.37	$982.35	$982.40