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	$151.93	3.322%	$156.9771	$156.98	$157.00	$157.00
Purchase #2	$102.82	9.800%	$112.8964	$112.90	$112.90	$112.90
Purchase #3	$220.40	11.558%	$245.8738	$245.87	$245.85	$245.90
Purchase #4	$170.40	10.664%	$188.5715	$188.57	$188.55	$188.60
Purchase #5	$171.63	9.698%	$188.2747	$188.27	$188.25	$188.30
Purchase #6	$63.96	11.527%	$71.3327	$71.33	$71.35	$71.30
Purchase #7	$88.30	9.834%	$96.9834	$96.98	$97.00	$97.00
7 purchase totals =	$969.44		$1,060.9096	$1,060.90	$1,060.90	$1,061.00