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	$144.36	7.415%	$155.0643	$155.06	$155.05	$155.10
Purchase #2	$94.76	4.531%	$99.0536	$99.05	$99.05	$99.10
Purchase #3	$31.56	7.501%	$33.9273	$33.93	$33.95	$33.90
Purchase #4	$21.41	12.431%	$24.0715	$24.07	$24.05	$24.10
Purchase #5	$173.54	6.750%	$185.254	$185.25	$185.25	$185.30
Purchase #6	$127.27	3.171%	$131.3057	$131.31	$131.30	$131.30
Purchase #7	$188.54	8.772%	$205.0787	$205.08	$205.10	$205.10
7 purchase totals =	$781.44		$833.7551	$833.75	$833.75	$833.90