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	$225.65	6.506%	$240.3308	$240.33	$240.35	$240.30
Purchase #2	$201.45	5.460%	$212.4492	$212.45	$212.45	$212.40
Purchase #3	$233.69	3.585%	$242.0678	$242.07	$242.05	$242.10
Purchase #4	$25.29	12.583%	$28.4722	$28.47	$28.45	$28.50
Purchase #5	$139.55	8.194%	$150.9847	$150.98	$151.00	$151.00
Purchase #6	$103.30	10.415%	$114.0587	$114.06	$114.05	$114.10
Purchase #7	$179.38	9.796%	$196.9521	$196.95	$196.95	$197.00
7 purchase totals =	$1,108.31		$1,185.3155	$1,185.31	$1,185.30	$1,185.40