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	$64.99	12.477%	$73.0988	$73.10	$73.10	$73.10
Purchase #2	$7.51	12.118%	$8.4201	$8.42	$8.40	$8.40
Purchase #3	$19.43	10.253%	$21.4222	$21.42	$21.40	$21.40
Purchase #4	$195.65	5.456%	$206.3247	$206.32	$206.30	$206.30
Purchase #5	$145.47	4.758%	$152.3915	$152.39	$152.40	$152.40
Purchase #6	$127.44	11.658%	$142.297	$142.30	$142.30	$142.30
Purchase #7	$143.33	5.311%	$150.9423	$150.94	$150.95	$150.90
7 purchase totals =	$703.82		$754.8966	$754.89	$754.85	$754.80