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	$167.76	10.379%	$185.1718	$185.17	$185.15	$185.20
Purchase #2	$127.35	5.444%	$134.2829	$134.28	$134.30	$134.30
Purchase #3	$31.59	7.218%	$33.8702	$33.87	$33.85	$33.90
Purchase #4	$208.40	3.337%	$215.3543	$215.35	$215.35	$215.40
Purchase #5	$27.99	13.449%	$31.7544	$31.75	$31.75	$31.80
Purchase #6	$65.89	11.575%	$73.5168	$73.52	$73.50	$73.50
Purchase #7	$140.46	7.355%	$150.7908	$150.79	$150.80	$150.80
7 purchase totals =	$769.44		$824.7412	$824.73	$824.70	$824.90