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	$113.78	11.667%	$127.0547	$127.05	$127.05	$127.10
Purchase #2	$79.39	12.288%	$89.1454	$89.15	$89.15	$89.10
Purchase #3	$193.27	8.261%	$209.236	$209.24	$209.25	$209.20
Purchase #4	$41.84	13.288%	$47.3997	$47.40	$47.40	$47.40
Purchase #5	$103.81	5.799%	$109.8299	$109.83	$109.85	$109.80
Purchase #6	$115.43	12.766%	$130.1658	$130.17	$130.15	$130.20
Purchase #7	$245.54	11.324%	$273.3449	$273.34	$273.35	$273.30
7 purchase totals =	$893.06		$986.1764	$986.18	$986.20	$986.10