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	$169.99	6.472%	$180.9918	$180.99	$181.00	$181.00
Purchase #2	$189.71	13.577%	$215.4669	$215.47	$215.45	$215.50
Purchase #3	$18.76	4.337%	$19.5736	$19.57	$19.55	$19.60
Purchase #4	$35.29	5.148%	$37.1067	$37.11	$37.10	$37.10
Purchase #5	$196.79	13.473%	$223.3035	$223.30	$223.30	$223.30
Purchase #6	$192.63	12.623%	$216.9457	$216.95	$216.95	$216.90
Purchase #7	$55.74	7.501%	$59.9211	$59.92	$59.90	$59.90
7 purchase totals =	$858.91		$953.3093	$953.31	$953.25	$953.30