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	$50.33	7.234%	$53.9709	$53.97	$53.95	$54.00
Purchase #2	$195.78	12.400%	$220.0567	$220.06	$220.05	$220.10
Purchase #3	$153.97	11.132%	$171.1099	$171.11	$171.10	$171.10
Purchase #4	$9.92	4.860%	$10.4021	$10.40	$10.40	$10.40
Purchase #5	$67.51	5.331%	$71.109	$71.11	$71.10	$71.10
Purchase #6	$117.54	12.145%	$131.8152	$131.82	$131.80	$131.80
Purchase #7	$112.58	9.661%	$123.4564	$123.46	$123.45	$123.50
7 purchase totals =	$707.63		$781.9202	$781.93	$781.85	$782.00