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	$201.56	4.300%	$210.2271	$210.23	$210.25	$210.20
Purchase #2	$83.61	13.789%	$95.139	$95.14	$95.15	$95.10
Purchase #3	$88.85	13.790%	$101.1024	$101.10	$101.10	$101.10
Purchase #4	$90.71	4.593%	$94.8763	$94.88	$94.90	$94.90
Purchase #5	$147.69	8.432%	$160.1432	$160.14	$160.15	$160.10
Purchase #6	$142.27	7.811%	$153.3827	$153.38	$153.40	$153.40
Purchase #7	$245.52	11.478%	$273.7008	$273.70	$273.70	$273.70
7 purchase totals =	$1,000.21		$1,088.5715	$1,088.57	$1,088.65	$1,088.50