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	$94.78	13.415%	$107.4947	$107.49	$107.50	$107.50
Purchase #2	$167.43	12.356%	$188.1177	$188.12	$188.10	$188.10
Purchase #3	$55.70	6.724%	$59.4453	$59.45	$59.45	$59.40
Purchase #4	$181.41	4.612%	$189.7766	$189.78	$189.80	$189.80
Purchase #5	$160.57	4.191%	$167.2995	$167.30	$167.30	$167.30
Purchase #6	$130.93	8.550%	$142.1245	$142.12	$142.10	$142.10
Purchase #7	$189.91	3.303%	$196.1827	$196.18	$196.20	$196.20
7 purchase totals =	$980.73		$1,050.4410	$1,050.44	$1,050.45	$1,050.40