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	$153.28	7.487%	$164.7561	$164.76	$164.75	$164.80
Purchase #2	$64.92	11.108%	$72.1313	$72.13	$72.15	$72.10
Purchase #3	$34.67	11.149%	$38.5354	$38.54	$38.55	$38.50
Purchase #4	$25.99	8.301%	$28.1474	$28.15	$28.15	$28.10
Purchase #5	$198.53	6.288%	$211.0136	$211.01	$211.00	$211.00
Purchase #6	$226.76	13.797%	$258.0461	$258.05	$258.05	$258.00
Purchase #7	$45.31	5.607%	$47.8505	$47.85	$47.85	$47.90
7 purchase totals =	$749.46		$820.4804	$820.49	$820.50	$820.40