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	$168.66	7.361%	$181.0751	$181.08	$181.10	$181.10
Purchase #2	$109.78	10.106%	$120.8744	$120.87	$120.85	$120.90
Purchase #3	$123.70	10.171%	$136.2815	$136.28	$136.30	$136.30
Purchase #4	$36.35	4.473%	$37.9759	$37.98	$38.00	$38.00
Purchase #5	$240.90	12.486%	$270.9788	$270.98	$271.00	$271.00
Purchase #6	$139.44	7.315%	$149.64	$149.64	$149.65	$149.60
Purchase #7	$121.89	4.242%	$127.0606	$127.06	$127.05	$127.10
7 purchase totals =	$940.72		$1,023.8863	$1,023.89	$1,023.95	$1,024.00