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	$80.58	10.763%	$89.2528	$89.25	$89.25	$89.30
Purchase #2	$205.26	8.769%	$223.2592	$223.26	$223.25	$223.30
Purchase #3	$18.57	11.565%	$20.7176	$20.72	$20.70	$20.70
Purchase #4	$171.33	8.598%	$186.061	$186.06	$186.05	$186.10
Purchase #5	$189.43	6.389%	$201.5327	$201.53	$201.55	$201.50
Purchase #6	$77.81	6.296%	$82.7089	$82.71	$82.70	$82.70
Purchase #7	$243.97	4.470%	$254.8755	$254.88	$254.90	$254.90
7 purchase totals =	$986.95		$1,058.4077	$1,058.41	$1,058.40	$1,058.50