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	$160.68	11.143%	$178.5846	$178.58	$178.60	$178.60
Purchase #2	$92.31	13.583%	$104.8485	$104.85	$104.85	$104.80
Purchase #3	$247.44	11.511%	$275.9228	$275.92	$275.90	$275.90
Purchase #4	$27.35	3.629%	$28.3425	$28.34	$28.35	$28.30
Purchase #5	$199.36	3.737%	$206.8101	$206.81	$206.80	$206.80
Purchase #6	$189.96	3.331%	$196.2876	$196.29	$196.30	$196.30
Purchase #7	$140.76	11.255%	$156.6025	$156.60	$156.60	$156.60
7 purchase totals =	$1,057.86		$1,147.3986	$1,147.39	$1,147.40	$1,147.30