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	$169.64	5.690%	$179.2925	$179.29	$179.30	$179.30
Purchase #2	$150.98	3.804%	$156.7233	$156.72	$156.70	$156.70
Purchase #3	$98.46	9.813%	$108.1219	$108.12	$108.10	$108.10
Purchase #4	$208.49	6.401%	$221.8354	$221.84	$221.85	$221.80
Purchase #5	$143.90	12.825%	$162.3552	$162.36	$162.35	$162.40
Purchase #6	$30.45	7.162%	$32.6308	$32.63	$32.65	$32.60
Purchase #7	$224.61	11.492%	$250.4222	$250.42	$250.40	$250.40
7 purchase totals =	$1,026.53		$1,111.3813	$1,111.38	$1,111.35	$1,111.30