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	$96.99	12.611%	$109.2214	$109.22	$109.20	$109.20
Purchase #2	$63.42	12.162%	$71.1331	$71.13	$71.15	$71.10
Purchase #3	$246.59	6.821%	$263.4099	$263.41	$263.40	$263.40
Purchase #4	$173.26	4.432%	$180.9389	$180.94	$180.95	$180.90
Purchase #5	$170.84	7.373%	$183.436	$183.44	$183.45	$183.40
Purchase #6	$170.27	12.262%	$191.1485	$191.15	$191.15	$191.10
Purchase #7	$102.35	8.728%	$111.2831	$111.28	$111.30	$111.30
7 purchase totals =	$1,023.72		$1,110.5709	$1,110.57	$1,110.60	$1,110.40