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	$156.86	13.539%	$178.0973	$178.10	$178.10	$178.10
Purchase #2	$189.62	5.366%	$199.795	$199.80	$199.80	$199.80
Purchase #3	$175.31	3.301%	$181.097	$181.10	$181.10	$181.10
Purchase #4	$160.96	8.350%	$174.4002	$174.40	$174.40	$174.40
Purchase #5	$70.55	11.211%	$78.4594	$78.46	$78.45	$78.50
Purchase #6	$98.96	3.591%	$102.5137	$102.51	$102.50	$102.50
Purchase #7	$83.35	9.457%	$91.2324	$91.23	$91.25	$91.20
7 purchase totals =	$935.61		$1,005.5950	$1,005.60	$1,005.60	$1,005.60