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	$55.34	7.143%	$59.2929	$59.29	$59.30	$59.30
Purchase #2	$204.33	9.174%	$223.0752	$223.08	$223.10	$223.10
Purchase #3	$146.35	11.226%	$162.7793	$162.78	$162.80	$162.80
Purchase #4	$161.30	6.265%	$171.4054	$171.41	$171.40	$171.40
Purchase #5	$154.92	8.148%	$167.5429	$167.54	$167.55	$167.50
Purchase #6	$171.36	7.416%	$184.0681	$184.07	$184.05	$184.10
Purchase #7	$148.98	9.172%	$162.6444	$162.64	$162.65	$162.60
7 purchase totals =	$1,042.58		$1,130.8082	$1,130.81	$1,130.85	$1,130.80