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	$96.97	5.355%	$102.1627	$102.16	$102.15	$102.20
Purchase #2	$70.26	4.625%	$73.5095	$73.51	$73.50	$73.50
Purchase #3	$220.82	9.526%	$241.8553	$241.86	$241.85	$241.90
Purchase #4	$110.69	8.428%	$120.019	$120.02	$120.00	$120.00
Purchase #5	$130.74	10.574%	$144.5644	$144.56	$144.55	$144.60
Purchase #6	$162.57	9.776%	$178.4628	$178.46	$178.45	$178.50
Purchase #7	$84.27	6.740%	$89.9498	$89.95	$89.95	$89.90
7 purchase totals =	$876.32		$950.5235	$950.52	$950.45	$950.60