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	$105.80	3.563%	$109.5697	$109.57	$109.55	$109.60
Purchase #2	$101.78	6.530%	$108.4262	$108.43	$108.45	$108.40
Purchase #3	$156.64	11.633%	$174.8619	$174.86	$174.85	$174.90
Purchase #4	$227.95	7.841%	$245.8236	$245.82	$245.80	$245.80
Purchase #5	$133.43	12.509%	$150.1208	$150.12	$150.10	$150.10
Purchase #6	$177.27	6.146%	$188.165	$188.17	$188.15	$188.20
Purchase #7	$70.88	3.295%	$73.2155	$73.22	$73.20	$73.20
7 purchase totals =	$973.75		$1,050.1827	$1,050.19	$1,050.10	$1,050.20