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	$89.64	6.786%	$95.723	$95.72	$95.70	$95.70
Purchase #2	$167.56	11.807%	$187.3438	$187.34	$187.35	$187.30
Purchase #3	$34.81	4.198%	$36.2713	$36.27	$36.25	$36.30
Purchase #4	$155.74	11.729%	$174.0067	$174.01	$174.00	$174.00
Purchase #5	$180.39	3.562%	$186.8155	$186.82	$186.80	$186.80
Purchase #6	$205.57	6.523%	$218.9793	$218.98	$219.00	$219.00
Purchase #7	$40.30	6.270%	$42.8268	$42.83	$42.85	$42.80
7 purchase totals =	$874.01		$941.9664	$941.97	$941.95	$941.90