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	$215.90	10.627%	$238.8437	$238.84	$238.85	$238.80
Purchase #2	$174.55	6.400%	$185.7212	$185.72	$185.70	$185.70
Purchase #3	$202.48	13.410%	$229.6326	$229.63	$229.65	$229.60
Purchase #4	$39.74	4.598%	$41.5672	$41.57	$41.55	$41.60
Purchase #5	$26.52	13.511%	$30.1031	$30.10	$30.10	$30.10
Purchase #6	$136.37	12.279%	$153.1149	$153.11	$153.10	$153.10
Purchase #7	$174.26	12.628%	$196.2656	$196.27	$196.25	$196.30
7 purchase totals =	$969.82		$1,075.2483	$1,075.24	$1,075.20	$1,075.20