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	$123.47	3.407%	$127.6766	$127.68	$127.70	$127.70
Purchase #2	$64.36	10.477%	$71.103	$71.10	$71.10	$71.10
Purchase #3	$144.28	12.865%	$162.8416	$162.84	$162.85	$162.80
Purchase #4	$81.64	9.680%	$89.5428	$89.54	$89.55	$89.50
Purchase #5	$195.31	8.358%	$211.634	$211.63	$211.65	$211.60
Purchase #6	$6.26	8.549%	$6.7952	$6.80	$6.80	$6.80
Purchase #7	$108.46	3.680%	$112.4513	$112.45	$112.45	$112.50
7 purchase totals =	$723.78		$782.0445	$782.04	$782.10	$782.00