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	$235.84	11.690%	$263.4097	$263.41	$263.40	$263.40
Purchase #2	$162.32	6.121%	$172.2556	$172.26	$172.25	$172.30
Purchase #3	$197.98	11.268%	$220.2884	$220.29	$220.30	$220.30
Purchase #4	$68.42	3.860%	$71.061	$71.06	$71.05	$71.10
Purchase #5	$142.68	9.870%	$156.7625	$156.76	$156.75	$156.80
Purchase #6	$39.46	7.428%	$42.3911	$42.39	$42.40	$42.40
Purchase #7	$18.79	3.365%	$19.4223	$19.42	$19.40	$19.40
7 purchase totals =	$865.49		$945.5906	$945.59	$945.55	$945.70