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	$96.36	4.163%	$100.3715	$100.37	$100.35	$100.40
Purchase #2	$212.92	10.426%	$235.119	$235.12	$235.10	$235.10
Purchase #3	$49.36	11.732%	$55.1509	$55.15	$55.15	$55.20
Purchase #4	$95.56	4.474%	$99.8354	$99.84	$99.85	$99.80
Purchase #5	$155.98	6.650%	$166.3527	$166.35	$166.35	$166.40
Purchase #6	$72.61	7.196%	$77.835	$77.84	$77.85	$77.80
Purchase #7	$205.85	6.343%	$218.9071	$218.91	$218.90	$218.90
7 purchase totals =	$888.64		$953.5716	$953.58	$953.55	$953.60