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	$221.92	3.426%	$229.523	$229.52	$229.50	$229.50
Purchase #2	$37.76	8.223%	$40.865	$40.87	$40.85	$40.90
Purchase #3	$81.85	11.343%	$91.1342	$91.13	$91.15	$91.10
Purchase #4	$115.26	4.580%	$120.5389	$120.54	$120.55	$120.50
Purchase #5	$34.78	6.781%	$37.1384	$37.14	$37.15	$37.10
Purchase #6	$100.46	10.163%	$110.6697	$110.67	$110.65	$110.70
Purchase #7	$142.27	4.122%	$148.1344	$148.13	$148.15	$148.10
7 purchase totals =	$734.30		$778.0036	$778.00	$778.00	$777.90