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	$186.79	5.403%	$196.8823	$196.88	$196.90	$196.90
Purchase #2	$13.96	5.725%	$14.7592	$14.76	$14.75	$14.80
Purchase #3	$198.64	12.488%	$223.4462	$223.45	$223.45	$223.40
Purchase #4	$204.69	8.445%	$221.9761	$221.98	$222.00	$222.00
Purchase #5	$92.36	12.134%	$103.567	$103.57	$103.55	$103.60
Purchase #6	$55.62	6.248%	$59.0951	$59.10	$59.10	$59.10
Purchase #7	$5.45	12.584%	$6.1358	$6.14	$6.15	$6.10
7 purchase totals =	$757.51		$825.8617	$825.88	$825.90	$825.90