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	$242.32	11.127%	$269.2829	$269.28	$269.30	$269.30
Purchase #2	$64.58	7.104%	$69.1678	$69.17	$69.15	$69.20
Purchase #3	$216.76	5.131%	$227.882	$227.88	$227.90	$227.90
Purchase #4	$246.34	12.142%	$276.2506	$276.25	$276.25	$276.30
Purchase #5	$73.92	5.599%	$78.0588	$78.06	$78.05	$78.10
Purchase #6	$19.46	6.576%	$20.7397	$20.74	$20.75	$20.70
Purchase #7	$190.82	5.246%	$200.8304	$200.83	$200.85	$200.80
7 purchase totals =	$1,054.20		$1,142.2122	$1,142.21	$1,142.25	$1,142.30