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	$171.62	8.242%	$185.7649	$185.76	$185.75	$185.80
Purchase #2	$119.68	6.229%	$127.1349	$127.13	$127.15	$127.10
Purchase #3	$159.90	9.215%	$174.6348	$174.63	$174.65	$174.60
Purchase #4	$170.31	11.765%	$190.347	$190.35	$190.35	$190.30
Purchase #5	$48.96	4.212%	$51.0222	$51.02	$51.00	$51.00
Purchase #6	$112.68	7.402%	$121.0206	$121.02	$121.00	$121.00
Purchase #7	$203.25	4.251%	$211.8902	$211.89	$211.90	$211.90
7 purchase totals =	$986.40		$1,061.8146	$1,061.80	$1,061.80	$1,061.70