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	$81.41	5.704%	$86.0536	$86.05	$86.05	$86.10
Purchase #2	$30.28	13.801%	$34.4589	$34.46	$34.45	$34.50
Purchase #3	$28.38	11.729%	$31.7087	$31.71	$31.70	$31.70
Purchase #4	$36.29	3.465%	$37.5474	$37.55	$37.55	$37.50
Purchase #5	$179.33	3.820%	$186.1804	$186.18	$186.20	$186.20
Purchase #6	$115.47	3.818%	$119.8786	$119.88	$119.90	$119.90
Purchase #7	$105.45	11.323%	$117.3901	$117.39	$117.40	$117.40
7 purchase totals =	$576.61		$613.2177	$613.22	$613.25	$613.30