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	$73.89	12.766%	$83.3228	$83.32	$83.30	$83.30
Purchase #2	$96.49	12.120%	$108.1846	$108.18	$108.20	$108.20
Purchase #3	$144.31	5.570%	$152.3481	$152.35	$152.35	$152.30
Purchase #4	$229.47	4.633%	$240.1013	$240.10	$240.10	$240.10
Purchase #5	$215.85	6.179%	$229.1874	$229.19	$229.20	$229.20
Purchase #6	$134.79	5.578%	$142.3086	$142.31	$142.30	$142.30
Purchase #7	$172.78	3.542%	$178.8999	$178.90	$178.90	$178.90
7 purchase totals =	$1,067.58		$1,134.3527	$1,134.35	$1,134.35	$1,134.30