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	$221.41	4.446%	$231.2539	$231.25	$231.25	$231.30
Purchase #2	$38.61	8.335%	$41.8281	$41.83	$41.85	$41.80
Purchase #3	$222.63	12.407%	$250.2517	$250.25	$250.25	$250.30
Purchase #4	$93.80	6.509%	$99.9054	$99.91	$99.90	$99.90
Purchase #5	$179.73	11.595%	$200.5697	$200.57	$200.55	$200.60
Purchase #6	$44.48	12.637%	$50.1009	$50.10	$50.10	$50.10
Purchase #7	$211.98	3.309%	$218.9944	$218.99	$219.00	$219.00
7 purchase totals =	$1,012.64		$1,092.9041	$1,092.90	$1,092.90	$1,093.00